Either parent may file a petition to modify a child custody order—but usually only when there is a substantial change in circumstances that affects the child (including changes in one or both of the parents’ lives) that justifies the court revisiting and possibly modifying the earlier child custody order.

The petition to modify child custody generally must be filed in the same court in which the parents’ divorce case was decided. But if the child lives in a different county or state, the courts of the county or state where the child lives may be the proper place to file a petition to modify a child custody order.

In Nevada, either parent has the right to file a petition to modify a child custody order. However, the court typically requires that there be a substantial change in circumstances that affects the welfare of the child before it will reconsider the existing custody arrangement. Such changes could include significant alterations in the living situation, financial status, or health of either parent, or other factors that impact the child's best interests. The petition to modify custody is generally filed in the same court where the original divorce and custody determinations were made. If the child has since moved to a different county or state, the petition may need to be filed in the jurisdiction where the child currently resides. The court in the new location would need to have proper jurisdiction to hear the case, which usually depends on the child having lived there for a sufficient period of time, often defined by the state's residency requirements for custody cases.